Inventories (Table) (Details) (USD $) In Millions, unless otherwise specified	Mar. 31, 2013	Dec. 31, 2012
Inventories
Separative work units inventory	$ 653.8	$ 880.9
Uranium inventory	400.6	703.7
Materials and supplies	6.4	8.6
Inventories	1,060.8	1,593.2
Separative work units owed to customers and suppliers	210.8	382.7
Uranium owed to customers and suppliers	263.9	567.3
Inventories owed to customers and suppliers	474.7	950.0
Separative work units net of liability	443.0	498.2
Uranium inventory net of liability	136.7	136.4
Inventories, net	$ 586.1	$ 643.2

Carrying amount (lower of cost or market) as of the balance sheet date of inventories less all valuation and other allowances. Excludes noncurrent inventory balances (expected to remain on hand past one year or one operating cycle, if longer).

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 210

-SubTopic 10

-Section S99

-Paragraph 1

-Subparagraph (SX 210.5-02.6(a))

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Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

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-Publisher FASB

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- Definition

Gross amount of products used directly or indirectly in the manufacturing or production process, which may or may not become part of the final product. May also include items used in the storage, presentation or transportation of physical goods.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher AICPA

-Name Accounting Research Bulletin (ARB)

-Number 43

-Paragraph 3

-Chapter 4

-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 210

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-Section S99

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-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

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-Publisher SEC

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-Number 210

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-Publisher AICPA

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-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

Reference 5: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Glossary Inventory

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Cost of SWU and uranium inventories owed related to the transfer of title from USEC to customer at fabricator whereby fabricator has elected to order less material from USEC than is required. Amounts owed are satisfied when fabricator orders future bulk deliveries.

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Inventory net of Liability

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Carrying amount as of the balance sheet date of separative work unit ("SWU") inventory. SWU is held as the SWU component of low enriched uranium. A SWU is the standard measure of uranium enrichment using a standard formula derived from the physics of enrichment. SWU costs are based on production costs and purchase costs. SWU inventory is valued at the lower of cost or market.

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Carrying amount as of the balance sheet date of uranium inventory. Uranium is held in the form of natural uranium and as the uranium component of low enriched uranium. Uranium inventory is valued at the lower of cost or market.

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Uranium inventory net of liability

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Uranium owed to customers and suppliers

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